Frequency multiplier circuits are widely employed in radio frequency (‘RF’) communication and sensor systems, for example. The expression ‘radio frequency’ is used in this specification to designate wireless communication frequencies without any specific upper limit and embodiments of this invention are usable up to millimetric wavelength frequencies and beyond.
A frequency multiplier circuit produces an output signal at a frequency which is a multiple of the frequency of an input signal applied to it. Typically, the output signal is a harmonic of the input signal, so that the output frequency is related to the input frequency by one or more factors of two. In the case of a frequency doubler circuit, the output signal is the harmonic whose frequency is double that of the input signal.
The article “A frequency doubler with high conversion gain and good fundamental suppression” by Gruson, F., Bergmann, G. and Schumacher, H. published in Microwave Symposium Digest, 2004 IEEE MTT-S International discloses a frequency doubler architecture applied to a K/sub u-/band frequency doubler which drives the local oscillator (‘LO’) port of a single-balanced Gilbert mixer.